Comment 5 for bug 1166181

The solution is that Bake checks vala-packages and adds these to the packages variable if they are not already defined.

e.g.

programs.foo {
    sources = foo.vala
    vala-packages = gtk+-3.0
}

Will automatically set programs.foo.packages to gtk+-3.0.

If you need to set the version of gtk+-3.0 then you can manually set programs.foo.packages - Bake will detect this and not modify it.

e.g.

programs.foo {
    sources = foo.vala
    vala-packages = gtk+-3.0
    packages = gtk+-3.0 >= 3.12
}

As a future enhancement we should make it possible to define versions in vala-packages (bug 1346171)